1. Field of the Invention
The present invention relates to a color adjustment method and related device for a display device, and more particularly, to a color adjustment method and related device for respectively adjusting each component of color space, e.g. HSI, of a composite video signal received by the display device.
2. Description of the Prior Art
With the advancement of communications and display technology, people can see favorite images, movies or TV programs by display devices, such as televisions or computers, and also have increasing demands on the display quality. For this reason, color adjustment techniques aim to simple control for users and precise adjustment to gain the best performance.
Human eyes can differentiate light of different wavelengths and have the largest response to light of three primary colors, red, green and blue. A general color display uses RGB color space to represent desired colors. Besides RGB, there are many popular color spaces that are color conversions of RGB, such as YIQ, YUV or YCbCr used in video system and CMYK used in color printing. In a video system, the transmitter usually transmits a composite video signal instead of RGB signal to the end user device. The composite video signal is composed of a luminance component representing the brightness of an image and a chrominance component representing the color information. For example, Y is the luminance component and Cb and Cr are blue-difference and red-difference chrominance components in YCbCr color space.
Please refer to FIG. 1, which is a color space diagram. As shown in FIG. 1, a color space is illustrated by six color axes of red, yellow, green, cyan, blue and magenta (RGBCMY). A conventional RGBCMY independent color adjustment method decides where a color signal is located in the color space according to RGB proportion of the color signal and then adjusts RGBCMY proportion independently. The RGBCMY independent color adjustment brings the best performance of the color signal but is not easily operated by users.
Another conventional color adjustment method generates a 2-dimensional look-up table for storing gain values corresponding to all possible chrominance signals and adjusts a chrominance signal to get the desired performance accordingly. However, the above methods only adjust hue and saturation of a color signal independently and do not adjust intensity of the color signal independently. In other words, a user cannot adjust contrast ratio of a displayed image by these conventional methods.